The present invention relates to a toothbrush having improved cleaning and abrasion efficiency while retaining acceptable wear characteristics.
In the oral hygiene field today, toothbrushing is ordinarily accomplished with a toothbrush which is adapted for use with a dentifrice composition, i.e., a toothpaste, which contains an abrasive substance or material designed to abrasively clean the teeth, i.e., to remove materials thereon, including pellicle, plaque, stains, dental calculus (tartar), and the like.
The current level of gum disease and tooth loss attributed to gum disease and gum retraction in adults, along with the incidence of gingivitis among adults, is an indication of the inefficiency of cleansing accomplished with those toothpaste/toothbrush combinations presently commercially available. In part, this poor cleaning is also due to the poor toothbrushing habits of a majority of adults which include; brushing only once a day, brushing improperly, and/or failing to brush long enough to effect adequate plaque, tartar removal, etc. Clearly, a more efficient toothbrush/toothpaste combination would be helpful.
In toothbrushing, the primary function of the bristle is to rub abrasive particles across the surface of the teeth and thereby remove by abrasive action deposits such as pellicle, stains, plaque, tartar and the like from tooth surfaces.
Accordingly, the tangential contact between toothpaste abrasive and surfaces of the teeth as influenced by toothbrush bristle tips during brushing has a major impact on toothbrushing efficiency.
Manufacturers of nylon bristle toothbrushes have provided in the past, a variety of toothbrushes designated as "soft," "medium," and/or "hard" to indicate the stiffness of the bristles. For a given thermoplastic polymeric composition, one factor, which predominantly determines bristle stiffness, is the diameter of the individual bristles. For example, with nylon 6,12 the "soft" bristles typically have a diameter between 0.008 and 0.009 inches; "medium" bristles have a diameter between 0.009 and 0.012 inches and "hard" bristles have a diameter greater than about 0.012 inches. Polybutylene terephtalate bristles are typically about 0.001 to 0.002 inches smaller in diameter due to the greater wet stiffness of this material over that of nylon 6,12. For all bristles used in toothbrushes, there is generally a manufacturing or grading tolerance of about .+-.0.0005 inches.
Soft bristles penetrate crevices between the teeth, while medium bristles and the hard bristles stabilize the soft bristles against bending as pressure is applied during brushing. The medium and hard bristles are believed to more effectively clean the surfaces of the teeth while the soft bristles achieve better penetration of crevices and are recommended for their gentleness to soft tissue.
Studies have shown that the most aggressive mechanical cleansing should be directed toward the tooth surface, with much less so toward the gingival surface and essentially none toward the base of the gingival sulcus. The basis for these observations is as follows:
1. The development of gingival inflammation and dental caries is most frequently caused by failure to remove dental plaque from the subgingival surface of the tooth and to a much lesser extent materia alba from the gingival surface in the subgingival space. Both dental plaque and materia alba can form within several hours of brushing and therefore frequent mechanical cleansing is essential. Materia alba, which consists primarily of an acquired bacterial coating and desquamated epithelial cells, leukocytes and a mixture of salivary proteins and lipids, is a soft sticky deposit less adherent than dental plaque. It can be flushed away with a water spray but more completely removed from the gingiva with mild mechanical cleansing.
2. Dental plaque is formed by oral microorganisms that synthesize harmful products that are destructive to the tooth and gums when not removed from the gingival sulcus. The toxins formed by these microorganisms cause cellular damage to the gingiva with subsequent inflammation (gingivitis) and eventually destruction of the supporting structures (periodontitis). When gingivitis occurs, vascular dilation, capillary proliferation, engorged vessels and sluggish venous return causes a stretched and thinned epithelium that is sensitive to mechanical trauma such as aggressive brushing.
3. Dental plaque with associated gingivitis also causes exposure of the root surface (recession) with increased occurrence of cavities (dental caries). Exposure of the root surfaces can also occur due to faulty brushing by repeated direct trauma to the base of the sulcus (gingival abrasion). When a pathologically deepened gingival sulcus (periodontal pocket) occurs, the pathological condition may become exacerbated because plaque can more readily occur. If dental plaque is not removed, calculus (tartar) is formed by mineralization of the bacterial plaque. Calculus can form within several hours of plaque formation. Calculus has a bacterial plaque coating and exacerbates gingivitis and gingival recession by both chemical irritation from the formed toxins and destruction from the mechanical irritation of the calculus mass. Subgingival calculus usually extends near but does not reach the base of periodontal pockets in chronic periodontal lesions. Calculus holds the plaque against the gingiva, and
4. Since materia alba can be removed by light mechanical cleansing and gingival inflammation causes thinning of the gingival epithelium the mechanical cleansing requirement of the gingival surface is much less than the requirement for removing dental plaque from the surface of the teeth.
Accordingly, a more efficient cleansing and abrading toothbrush, which fulfills the foregoing requirements while protecting the base of the gingival sulcus, is desirable.
Review of Prior Art
Toothbrush bristles have come a long way from the curly-tusked swine hair they were made from prior to World War II. First was the introduction of nylon synthetic fiber in 1938. The popular round toothbrush bristle style introduced in 1938 is used today in more than 50% of the premium toothbrushes used worldwide.
Since 1938 nearly all major toothbrush marketers have developed innovative "cosmetic" features which make their toothbrush offerings unique at the retail shelf These features included: colors, packaging, innovative handle and head designs, trimming alternatives, various tufting arrangements, various bristle lengths, bristle diameters, etc. Whatever the cosmetic feature(s) promoted, these commercial toothbrushes have typically relied on the basic cylindrical bristle with rounded tips for abrasive/tooth surface contact. See for example, U.S. Pat. Nos. 3,217,074, 4,898,193, 4,927,281, 4,993,440, 5,020,552 and 5,511,275.
Recently, unique bristle designs have been designed and commercialized reportedly to improve plaque removal, interdental cleaning, gum care and durability. All of these recent innovations also rely on the classic bristle tip (usually rounded) abrasive contact with the tooth surface to affect cleaning. See Tynex.RTM. Shapes and Textures Toothbrush Filaments" . . . because specialized cleaning starts at the tips" (H-50102) published by the DuPont Company, Washington WV 26181, 1995. This publication is hereby incorporated herein by reference.
Summarized below in Table 1 are some recent industry approaches to various consumer toothbrush needs where toothbrush bristle shape, and texture are varied to provide "specializing cleaning". Note: These approaches are based on bristle tip/toothpaste abrasive interaction to achieve cleansing and abrasion of tooth surfaces.
TABLE 1 ______________________________________ Consumer Feature to Address Recommended Tynex .RTM. Need Consumer Need Bristle Construction ______________________________________ Interdental Fine tips able to reach Feathered Cleaning farther between teeth. More bristles per tuft Hexagonal working with every stroke. Plaque Higher surface contact area Hexagonal Removal increased ability to hold toothpaste at tips. Feathered Higher functional Grainy, Co-Extruded abrasiveness. Compliance with Bass brushing Methods. Rectangular Healthy Gums Gentleness to the gums Feathered, Rectangular End-rounded tips All styles More surface area to Hexagonal distribute force applied to brush Softness of tips Feathered Durability Improved Wear Technology All Styles Superior bristle integrity Hexagonal ______________________________________
Various cross-sectional geometric bristle shapes have been developed to enhance the performance of toothbrushes in general. For example, U.S. Pat. No. 2,317,485 teaches that circular cross-sectional bristles do not pack as efficiently as other shapes such as triangles, squares, pentagon's etc. U.S. Pat. No. 2,876,477 utilizes polygons with a concave contour on each side to maximize interstitial spacing. The corners of the bristle sides serve as scrapers for the bristles. The multi-fluted sides of these bristles are designed to function in a manner analogous to scaly natural bristles.
Bristle brushes other than toothbrushes with various cross-sectional shapes are disclosed in U.S. Pat. Nos. 4,386,325; 4,898,193; 4,167,794, 5,020,551 and 5,396,678. U.S. Pat. No. 5,396,678 teaches toothbrush bristles having a rectangular cross-sectional shape. U.S. Pat. No. 5,020,551 discloses various bristle cross sections including: solid circular, hollow circular, cruciform, and multilobal. U.S. Pat. No. 4,898,193 teaches multi-ridged polygon bristles for combing eyelashes and for applying mascara to the eyelashes. This reference teaches that the sides of the polygon bristle can curve inwardly. Similarly U.S. Pat. No. 4,381,325 discloses a liquid-retaining synthetic bristle having an acute ridgeline extending longitudinal on its surface. The bristle has at least one convex portion. The arcuate concave grooves were shown to retain more liquids such as India ink than non-ridged comparable brushes.
U.S. Pat. No. 3,613,143 discloses toothbrushes with abrasive impregnated bristles of two cross-section designs, i.e., generally circular and polygon with the latter described as having longitudinal groove arrangements.
U.S. Pat. No. 4,167,794 discloses rounded bristles having shovel-like distal ends for more effective plaque removal.
U.S. Pat. No. 4,958,402 teaches fiber-flocking synthetic bristles as a means of retaining the substance to be applied and more effectively distributing the substance on the surface to be treated. These fiber-coated bristles are taught for use in interdental cleaning. Similarly, U.S. Pat. No. 5,195,546 teaches having a gentle random and irregular wavy configuration along the length of the bristles for the improved application of powder to surfaces.
U.S. Pat. No. 2,312,828 teaches improved abrasive tooth surface contact by forming in the working face of the brush a longitudinal groove or channel of a size to receive and hold a strip of paste squeezed from the tube, this groove or channel being completely closed at its sides and ends by the outside longitudinal and transverse rows of full length bristles, so that the paste or powder deposits cannot fall from the brush.
U.S. Pat. No. 2,599,191 teaches improved toothbrushes for treating gum disease where the bristles are looped resulting in a smooth "side surface" contact with teeth and soft tissue.
U.S. Pat. No. 2,845,649 teaches a small diameter nylon bristle with higher tuft count produces a "sweeping action" as distinguished from traditionally "coarse" toothbrushes. It is suggested this sweeping action is gentler on soft tissue.
U.S. Pat. No. 4,993,440 describes a brush for the application of cosmetic products such as mascara, where the bristle has a capillary channel extending from the base to the tip. This channel has a V-shaped or U-shaped cross section designed to hold the mascara.
Toothbrush constructions of various types have been disclosed throughout the prior art to accommodate access to various components of an individual's mouth during a toothbrushing procedure. Such toothbrushes are exemplified in U.S. Pat. No. 4,800,608 wherein the bristle head is formed having a fixed obtuse angle. See also U.S. Pat. Nos. 3,072,944; 3,188,643; 3,263,258; 5,346,678; 5,274,873; 5,335,384; 5,355,546; 5,360,025; 5,497,526 and 5,511,275.
U.S. Pat. No. 4,729,142 sets forth a toothbrush head having the bristles directed towards the medial center of the toothbrush head.
U.S. Pat. No. 4,852,202 sets forth a toothbrush head having angulated bristles, wherein the bristles include first bristles having an orthogonal orientation relative to the toothbrush head, with a plurality of secondary bristles mounted at a generally forty-five degree angle relative to the toothbrush head.
U.S. Pat. No. 3,032,230 teaches bristles with a polygon cross-section having at least two acute angles that impart a "scraping" effect on the teeth. U.S. Pat. No. 3,214,777 teaches bristles with a rectangular cross-sectional area.
See also U.S. Pat. Nos. 2,088,839; 3,295,156; 3,722,020; 3,939,520; 4,167,794; 3,217,074; 3,238,553 and 4,927,281.
The prior art also teaches that generally, most adult toothbrushes have between 2000 and 3000 bristles with between 2300 and 2600 most popular. These bristles are usually arranged in three to five rows with about 15 tufts/row. In contrast, a child's toothbrush may have only three rows with approximately 10 tufts in each row.
Until the present invention, all toothbrush bristle constructions described in the prior art, including round, round/hollow, multi-lobal, rectangular, hexagonal, etc. type bristles could be characterized as effecting only tangential "point" contact between the bristle tip, the abrasive, and the surface. The present invention represents the next advance in this area, providing greater contact between these elements.